Arrhythmia is a variation from the normal rhythm of the heart beat and generally represents the end product of abnormal ion-channel structure, number or function. Both atrial arrhythmias and ventricular arrhythmias are known. The major cause of fatalities due to cardiac arrhythmias is the subtype of ventricular arrhythmias known as ventricular fibrillation (VF). Conservative estimates indicate that, in the U.S. alone, each year over one million Americans will have a new or recurrent coronary attack (defined as myocardial infarction or fatal coronary heart disease). About 650,000 of these will be first heart attacks and 450,000 will be recurrent attacks. About one-third of the people experiencing these attacks will die of them. At least 250,000 people a year die of coronary heart disease within 1 hour of the onset of symptoms and before they reach a hospital. These are sudden deaths caused by cardiac arrest, usually resulting from ventricular fibrillation.
Atrial fibrillation (AF) is the most common arrhythmia seen in clinical practice and is a cause of morbidity in many individuals (Pritchett E. L., N. Engl. J. Med. 327(14):1031 Oct. 1, 1992, discussion 1031-2; Kannel and Wolf, Am. Heart J. 123(1):264-7 Jan. 1992). Its prevalence is likely to increase as the population ages and it is estimated that 3-5% of patients over the age of 60 years have AF (Kannel W. B., Abbot R. D., Savage D. D., McNamara P. M., N. Engl. J. Med. 306(17):1018-22, 1982; Wolf P. A., Abbot R. D., Kannel W. B. Stroke. 22(8):983-8, 1991). While AF is rarely fatal, it can impair cardiac function and is a major cause of stroke (Hinton R. C., Kistler J. P., Fallon J. T., Friedlich A. L., Fisher C. M., American Journal of Cardiology 40(4):509-13, 1977; Wolf P. A., Abbot R. D., Kannel W. B., Archives of Internal Medicine 147(9):1561-4, 1987; Wolf P. A., Abbot R. D., Kannel W. B. Stroke. 22(8):983-8, 1991; Cabin H. S., Clubb K. S., Hall C., Perlmutter R. A., Feinstein A. R., American Journal of Cardiology 65(16):1112-6, 1990).
WO99/50225 discloses a class of aminocyclohexylether compounds as useful in the treatment of arrhythmias. Some of the new aminocyclohexylether compounds have been found to be particularly effective in the treatment and/or prevention of AF. However, synthetic methods described in WO99/50225 and elsewhere were non-stereoselective and led to mixture of stereoisomers (see e.g., FIGS. 1-3). As active pharmaceutical compounds, it is often desirable that drug molecules are in stereoisomerically substantially pure form. It may not be feasible or cost effective if the correct stereoisomer has to be isolated from a mixture of stereoisomers after a multi-step synthesis. Therefore, there remains a need in the art to develop method for the preparation of stereoisomerically substantially pure trans-aminocyclohexyl ether compounds as well as method for the preparation of stereoisomerically substantially pure cis-aminocyclohexyl ether compounds.
Although WO 2003/105756 describes a method of stereoselectively preparing a trans-1,2, di-substituted cycloalkane, the method disclosed therein requires a trans-1R,2R di-substituted cycloalkane. In an alternate embodiment, disclosed is a method that requires reacting a cis-2-substituted cycloalkanol with a galactose derivative. These requirements may not be generally feasible and/or amenable to large scale manufacture processes. The present invention generally does not have such limitations.